The present invention relates to self-processing photographic film units, also called instant film units. More specifically, the invention relates to a processing sleeve for use with a dye-donating film sheet to provide borderless photographic prints.
Typically, instant film is processed by covering the film sheet with a second sheet and distributing a viscous processing fluid therebetween. The fluid permeates the photosensitive layers of the film sheet and initiates development of the latent image. Development, in turn, controls diffusion of an imagewise distribution of materials, such as dyes, which transfer to an image-receiving layer where they form the visible picture.
Instant film units having the above general characteristics are well known in many different formats. Those of most interest are referred to as "peel-apart" film units, because the image-receiving layer is in the second sheet, called the image-receiving sheet, and that sheet is peeled apart from the remainder of the film unit after processing. The finished picture is supported in the image-receiving sheet, and the remainder of the film unit is discarded.
In accordance with one type of peel-apart film unit, adapted to be handled as an individual film unit, rather than in a multi-unit pack, a processing sleeve is provided to protect the film sheet prior to the intended exposure and to hold the film sheet and image-receiving sheet in superposition during processing. The film sheet is removed from the sleeve for exposure and returned for processing. After processing, the sleeve is torn open and the image-receiving sheet is peeled away from the film sheet in the usual manner for peel-apart film units.
U.S. Pat. No. 3,586,501, issued in the name of W. E. Norquist on June 22, 1971, depicts an example of a film unit of this type, including an opaque sleeve which carries the image-receiving sheet, a pouch for supplying the processing fluid, side rails for spacing the film and image-receiving sheets apart to control the depth of the distributed processing fluid and a mask for framing the final picture. The opaque sleeve acts as a miniature dark room that contains the film sheet and protects it from fogging. In use: (1) the entire film unit, i.e., the sleeve with the film sheet inside, is loaded into a camera; (2) the film sheet is held by the camera while the sleeve is withdrawn through a light-locked exit slot to uncover the film sheet for exposure; (3) the film sheet is exposed; (4) the sleeve is returned to its position in the camera covering the film sheet; and (5) the entire film unit is transported from the camera through a pair of opposed pressure rollers. The roller pressure ruptures the pouch, distributes the processing fluid, and initiates processing of the film sheet. After a suitable period for development and dye transfer, the sleeve is torn open, the image-receiving sheet is peeled away to provide the finished picture, and the remainder of the film unit is discarded.
A more recently developed processing sleeve, described in the cross-referenced patent application, includes a film retaining sheet doubled over along its lateral edges and coupled to the image-receiving sheet to form a pocket. The film sheet, after it is exposed, is inserted into the pocket in registration with the image-receiving sheet. The image-receiving sheet forms an outermost portion of one face of the sleeve and is directly accessible so that, after processing, it can be stripped from the remainder of the sleeve to provide the final picture.
Although previously known processing sleeves have been satisfactory for their intended purpose, most include a relatively large number of parts, are undesirably complex to manufacture, and are difficult to use. The processing sleeve of the above-mentioned application overcomes many of these disadvantages, but is not particularly conducive to the production of borderless prints.